generate ecdsa public key from an input public key (#219)

crypto/ecdsa.go

@@ -67,6 +67,11 @@ func ECDSAKeyPairFromKey(priv *ecdsa.PrivateKey) (PrivKey, PubKey, error) {
 	return &ECDSAPrivateKey{priv}, &ECDSAPublicKey{&priv.PublicKey}, nil
 }
 
+// ECDSAPublicKeyFromPubKey generates a new ecdsa public key from an input public key
+func ECDSAPublicKeyFromPubKey(pub ecdsa.PublicKey) (PubKey, error) {
+	return &ECDSAPublicKey{pub: &pub}, nil
+}
+
 // MarshalECDSAPrivateKey returns x509 bytes from a private key
 func MarshalECDSAPrivateKey(ePriv ECDSAPrivateKey) ([]byte, error) {
 	return x509.MarshalECPrivateKey(ePriv.priv)

crypto/ecdsa_test.go

@@ -1,6 +1,7 @@
 package crypto
 
 import (
+	"crypto/ecdsa"
 	"crypto/rand"
 	"testing"
 )
@@ -94,3 +95,48 @@ func TestECDSAMarshalLoop(t *testing.T) {
 	}
 
 }
+
+func TestECDSAPublicKeyFromPubKey(t *testing.T) {
+	ecdsaPrivK, err := ecdsa.GenerateKey(ECDSACurve, rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	privK, _, err := ECDSAKeyPairFromKey(ecdsaPrivK)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	data := []byte("Hello world!")
+	signature, err := privK.Sign(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pubKey, err := ECDSAPublicKeyFromPubKey(ecdsaPrivK.PublicKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ok, err := pubKey.Verify(data, signature)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !ok {
+		t.Fatal("signature didn't match")
+	}
+
+	pubB, err := MarshalPublicKey(pubKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	pubNew, err := UnmarshalPublicKey(pubB)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !pubKey.Equals(pubNew) || !pubNew.Equals(pubKey) {
+		t.Fatal("keys are not equal")
+	}
+}